Analog-to-digital converter



Dec. 10, 1968 T, R, TRILUNG 3,416,152

ANALOG -TO-DIGI'I'AL CONVERTER Filed April 22, 1964 2 Sheets-Sheet 2 J5954 5a AMPLlFlER 2 55 VERTICAL ANALOG DEFLECTION SIGNAL SWEEP CLOCKVOLTAGE PULSE GENERATOR GENERATOR F' 3 l LOGIC GATE 74 v 71 1 L-' COUTPUT I v ghifi ANALYZER b n n rl [3 n r1 64 73 c V dc} M e fl l'U"U'lf1: f "E Fig 5 Fig 6 B1 84 F lg. 4

SWEEP souRcE VOLTAGE PULSE l LOGIC GATE INVENTOR. F lg, 8 THEODORE R.TRILLING [WE/2A ATTORNEYS United States Patent 3,416,152ANALOG-TO-DIGITAL CONVERTER Theodore R. Trilling, 15 Hunt Road,Levittown, Pa. 19056 Filed Apr. 22, 1964, Ser. No. 361,916 11 Claims.(Cl. 340347) ABSTRACT OF THE DISCLOSURE A cathode ray tube or solidstate device is utilized in conjunction with any of a plurality ofmatrices on which a beam of carriers is impinged to thereby convert ananalog signal to a series of digital outputs expressive of that analogsignal depending upon the particular configuration of the matrix and thecontrol circuitry utilized to deflect the beam of carriers.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

The present invention relates to analog-to-digital converters and moreparticularly to a cathode ray tube and solid state device utilizing amatrix on which a beam. of carriers is entrained to convert an analogsignal to a series of digital outputs expressive of that analog signal.

It is desired in many applications to convert an analog signal ofvarious kinds into a digital output of various kinds, for example, intoa pulse train wherein either the width of the pulse, the height of thepulse, or the sequence of a series of pulses is indicative of the heightof the analog signal at that instant. For example, it may be desired toconvert a voice signal into a series of pulses trains for the purpose ofcoding. Or it may be desired to have a series of outputs, each outputbeing indicative of a certain height of the incoming analog signal.Prior art devices in this cfield have shared the common failing of notbeing fast enough. For example, an attempt to break up a voice signalinto a digital form may achieve only conversion of the low frequencycomponents of the voice with substantial distortion of the voice signalor garbling of the message.

The present invention provides a very high speed means for converting ananalog signal to a digital signal wherein the digital increments ofsignal comprise a small part of each cycle even at the highestfrequencies present. To attain this, the invention provides a cathoderay tube wherein the analog signal is inserted on one or both of thedeflecting means and a matrix of conducting spots are placed on the faceof the tube and are connected to issue an output current upon incidenceof a beam from the electron gun of the tube. The invention also providesa solid state device which is an equivalent of a cathode ray tube, inwhich a beam of carriers is issued through the solid state device to amatrix of collector spots on one face of the solid state device. Thecathode ray tube and solid state device of the present invention havebeen discovered to be extremely versatile and are usfeul for a number ofassociated devices in addition to the translation of a voice signal intoa pulse train. Others may be mentioned, such as a shaft encoder, phasecomparator, delay line, multiplex discriminator, and other uses, as willappear.

Accordingly, it is an object of the present invention to provide acathode ray tube with a matrix of conducting spots on the inside face ofthe tube with the digital output of the tube being a function of theanalog input.

Another object of the invention is to provide a solid state devicehaving therein a beam of carriers on the collector matrix thereof withthe digital output of the Ice matrix being a function of an analog inputinto the device.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawings wherein:

FIG. 1 shows a view in section of a cathode ray tube according to theinvention;

FIG. 2 shows a view in section of a solid state device according to thepresent invention;

FIG. 3 shows a schematic diagram of an analog-todigital convertercircuit of the present invention using either the cathode ray tube ofFIG. 1 or the solid state device of FIG. 2;

FIG. 4 shows a detail of a matrix of an embodiment of the invention withan associated output amplifier;

FIG. 5 shows another embodiment of the invention comprising a pulseheight analyzer;

FIG. 6 shows typical waveforms in the outputs of the embodiment of FIG.5;

FIG. 7 shows another embodiment of the invention comprising a pulsedelay line;

FIG. 8 shows a typical waveform in the output of the embodiment of FIG.7;

FIG. 9 shows a further embodiment of the invention comprising a phasecomparator;

FIG. 10 shows another embodiment of the invention comprising a multiplexdiscriminator;

FIG. 11 shows another embodiment of the invention comprising a shaftencoder for determining the angular position of a shaft and producing adigital output in response thereto;

FIG. 12 shows a shaft whose angular position is desired to be expressedin the shaft encoder of FIG. 11; and

FIG. 13 shows the construction of a matrix spot and lead of the cathoderay tube of FIG. 1.

Turning now to the drawings, FIG. 1 represents a cathode ray tube 21which is conventional except for the target area. A cathode 22 emits astream of electrons which is controlled by a grid 23 and focused by afocusing ring 24 on a plate 25 which in this case is the matrix of theinvention. Cathode 22, grid 23 and focusing ring 24 comprise an electrongun issuing a beam of electrons 26 onto the plate 25. A voltage supply,not shown, is provided between the cathode 22 and the plate 25, placingplate 25 at a very high positive voltage relative to the cathode 22. Theconstruction of the cathode ray tube is not shown in detail becausecathode ray tubes are known in the art, and the construction of thiscathode ray tube is well known in the art except for the platecomprising the matrix of the present invention. Also, are showndeflecting plates 27 across which a voltage is placed to deflect thebeam in order to place it in the desired position on the matrix 25.Another pair of deflectirig plates may be placed perpendicularly to theshown pair 27 for horizontal as well as vertical deflection. It will beunderstood that although electrical deflection means are shown,electromagnetic deflection may also be used, which would constitute apair of coils placed across the tube. The choice of electrical orelectromagnetic deflection means will depend on the amount of precisionand the amount of speed of the deflection which is desired. In general,the electrical means provides greater speed of response to an analogsignal, while the electromagnetic means provides higher precision. Forhigh frequency responses one would generally select electricaldeflection means, but for precision work one would generally selectelectromagnetic deflection means.

In FIG. 2 is shown a solid state equivalent of the cathode ray tube. Thedevice comprises an emitter 31,

base 32, intrinsic core 33 and collector spots 34. The emitter 31 iscomposed of a doped semiconductor material providing polarity in onedirection, either N or P type material. The base 32 will be of theopposite polarity, as is understood by persons in the art. The core 33is a pure intrinsic semiconductor material that is not doped either N orP type. The collector spots 34 will be doped into the face of theopposite end of the core 33 and will be of the same polarity as theemitter 31. A voltage supply 35 is connected between the collectors 34and the emitter 31. A bias voltage 36 is provided between the base 32and the emitter 3 1. The polarity of these voltage supplies will dependupon the polarity of the semiconductor elements 31, 32 and 34, as willbe understood by a person in the art. A stream of carriers will issuefrom the emitter through the base and through the intrinsic core tocontact the collector matrix 34. This beam of carriers, which may beeither holes or electrons, depending on the chosen polarity, may befocused by a focusing ring 37. The beam may also be deflected by a pairof deflecting plates 38. It will be understood that plates may beprovided both horizontally and vertically for horizontal and verticaldeflection. It will also be understood that cit-her electrical means orelectromagnetic means may be provided as in the cathode ray tube ofFIG. 1. The outputs from the collector spots 34 which form the matrix ofthe device, Will be led through a set of logic circuits with an outputindicator indicated generally at 39. \This output indicator may eitherbe a set of dials giving a digital expression of the signal or it may bein the form of a connection to another part of the circuit providing apulse train expressing the digital signal. It will be seen that thesolid state device of FIG. 2 is generally useable for all of the uses ofthe cathode ray tube of FIG. 1.

The operation of the converter may be illustrated by reference to MG. 3,in which is shown a matrix 51 on an end plate 52 of the converter. Theanalog signal 53 is fed into the vertical deflection means 54 whichplaces a voltage proportional to the analog signal across the verticalplates 55 to deflect the beam up and down on the matrix 51 in accordancewith the analog signal. A sweep voltage generator 56 causes a horizontalvoltage on horizontal deflection plate 57 which causes the beam to passacross the tube at a relatively slow rate and then revert to the firstside of the beam at a relatively fast rate in response to a pulse from aclock pulse gen erator 58. A voltage causing the beam to sweephorizontally across the tube may be either a sawtooth voltage or astaircase voltage depending upon the application. Because of thesimultaneous application of the sweep voltage and the analog signal fedinto the vertical deflection means, the position of the beam at variouspoints in the matrix at various points in time will produce an outputwhich is a pulse train or a series of pulse trains which are areflection of the analog signal fed into the converter. These pulsetrains may be fed into an amplifier 59 and the amplified signal fed to alogic gate 60 into which may be optionally fed also a series of clockpulses from clock pulse generator 58 for the purpose of sampling thepulse train. When used in this manner, the logic gate 60 wil be of theand gate type. "The output from logic gate 60 will be a sampled pulsetrain, the incidence of which is indicative of the analog signal.

FIG. 4 illustrates a specific matrix which may be used in the converteras shown in FIG. 3. A matrix 61 is arranged in a code called a Graycode. This matric will be in the case of the cathode ray tube a printedlayer on the inside of the face of the tube and in the case of the solidstate device will be a continuous arrangement of doped collectormaterial on the end of the intrinsic core with a layer of metallicmaterial laid directly over the doped collector material. It will beseen that there will be a current out of the matrix when the beam ofcarriers either in the tube or solid State device contacts someconducting portion of the matrix. It will also be seen that as the beamsweeps across the matrix, the arrangement of conducting andnonconducting portions of the matrix at that level is unique to thatlevel, so that the output train of square pulses will be a unique outputfor the particular level of the analog signal at that point. The Graycode shown provides code levels, and a matrix of 100 levels as shownwould typically be reduced to a printed metal matrix on the inside faceof the cathode ray tube approximately one inch high. In a cathode raytube of approximately four inches by four inches operating area thereWould be room for approximately 300 levels of signal. The matrix wouldbe approximately one-tenth of an inch wide and across the face of thetube there would be room for approximately 30 successive matrices. Onesweep of the voltage across the tube would, therefore, give 30successive coded outputs of the analog signal. In this code it isimportant that the repetition of bits or code readings from the matrixbe at least ten times the highest frequency of the analog signal desiredto be analyzed. For an analog signal corresponding to a voice inputwhere the highest frequency is approximately five kilocycles to tenkilocycles, a typical sampling rate would be 100,000 hits per second.Since a typical number of matrices on the face Of the tube might be 25,this requires a sweep frequency of 4,000 sweeps per second. These areexamples, and for other uses other parameters would be chosen. In thisembodiment all of the matrices would be tied together at their tops anda single output would be led out to an amplifier 59 which in thisembodiment comprises a transistor 62 connected to a minus source ofvoltage, in which the output 63 appears across a load resistance 64. Theoutput of this embodiment as shown would be in the form of a pulse widthmodulated train of pulses in which the width of the pulses and theirposition would determine the code level. LIf desired, the pulse widthmodulated code may be translated to a pulse code modulated code by theinsertion of a clock pulse from clock pulse generator 58. There would bean inserted clock pulse during each occurrence of a square pulse ornonpulse on the matrix 61. This converts the pulses of variable width toa series of pulses of equal width with position of pulse only beingindicative of the level of the signal. The Gray code selected and shownin RIG. 4 is one which provides a minimum number of changes of positionfrom one level to the next. One may instead use a. binary code, or onemay take a random code in order to provide a pulse train indicative of avoice signal which can only be translated back into a voice signal byone having a copy of that code. Another variation on this general themewould be a matrix arranged in the Morse code wherein the signal input isa series of voltage levels corresponding to various letters in which theoutput automatically translates the letter input into the correspondingdot-dash code.

FIG. 5 shows an embodiment of the invention which is known as a pulseheight analyzer. In this embodiment, there is no sweep voltage. Ananalog signal 71 is placed on vertical deflection plates 72. A matrixcomprising a single column of conducting spots 73a-f is placed on theconverter and each of the spots is separately connected to an outputanalyzer 74. The analog signal will cause the beam to ride up and downon this single column 73 without moving horizontally. The result will bea number of outputs equal to the number of spots in the column, whereinthe width of the pulse in each output is dependent upon the amount oftime that the analog signal dwells in the vicinity of that spot. Theoutlay analyzer 74 may be a logic store or computer memory or anindicator, since the output is already pulse height analyzed. If theinput is a switching address, the output will be a series of currents toa series of loads to be turned on and off in response to the address. Inthis embodiment, the tube is a switching tube. This can be extended to atwo-dimensional matrix.

Although six spots are shown in the matrix of FIG. 5, it will beunderstood that potentially hundreds of separate levels may be set forthin a column on the face of a tube. It is important also to note that inthis embodiment the spots on the face of the tube are not connectedtogether as in the code matrix of FIG. 4, but each lead must be ledseparately out of the tube and into the analyzer. The manner in whichthis is done is shown in FIG. 13, to be described below.

In FIG. 7 is another embodiment of the invention identified as a pulsedelay line. In this embodiment a sweep voltage 81 is applied across apair of deflection plates 82. A matrix 83 on the face of the tubeconsists of a single row of spots 8341-7 and there will be an outputfrom each as the beam sweeps across it. The sweep voltage 81 istriggered by a source pulse 84 which may also send the same pulse to alogic gate 85. One or more output pulses from matrix 83 may be selectedby a selector switch 86 which sends the selected output pulse or pulsesto the logic gate 85. In this embodiment, logic gate 85 is of the ortype. The pulse delay line of this embodiment has a number ofapplications. It may be, for example, desired to have an input pulsefollowed by a certain period of time by a second pulse. This is commonlyused in radar in connection with a ranging device. In anotherapplication one may have a series of voltage inverters in a stepped wavevoltage output power supply, and it may be desirable to operate thevoltages out of phase with each other by a predetermined amount. Byconnecting the inverters of the various voltage supplies to diflferentoutputs from the matrix 83 and triggering the entire assembly by asingle oscillator input to sweep voltage 81, it will be seen that thereis provided a series of output pulse trains of the same frequency as theinput and out of phase with each other by a predetermined amountdependent upon the separation of the spots in the matrix from eachother. The timing of the pulse outputs may also be finely adjusted byvarying the rate of rise of the sweep voltage 81. This provides a fineadjustment, whereas the selection of the particular outputs will providea coarse adjustment. In another application one may wish to delay aninput train of pulses by a certain amount in order to synchronize thistrain of pulses with another frequency. In this application, the sourcepulse would be fed to the sweep voltage 81 only and not to the logicgate 85. FIG. 8 shows a typical waveform from the delay line of FIG. 7wherein 91 is the input pulse and 92 is the output pulse delayed frompulse 91 by delay time T FIG. 9 shows still another embodiment of theinvention, this one comprising a phase comparator. Two sine waves 1; andf of the same frequency are desired to be compared to determine therelative phase angle between them. The two sine waves are placed acrossthe pairs of deflection plates 101 and 102, respectively. The matrix 103of the embodiment includes a column of dots bisecting the center of theface. Extending horizontally on each side of each dot is a line ofconducting material, and each dot and each line have separate outputsleading to output logic circuits and readout 104. The output logiccircuits receiving the outputs from the various lines and dots on theface of the converter determine three significant values: A, the upperdot contacted by the beam, B the uppermost line contacted by the beam,and B, the lowermost line contacted by the beam. The logic circuits willalso be capable of determining in what order these three values occur.The logic circuits in themselves are standard digital logic circuits andare not shown here. From the basic mathematical characteristics of anellipse formed by two sine waves, the phase angle between the two sinewaves may be calculated from the following relationship:

sin 0:B/A

If B is on the right side and B is on the left side, as shown, thereadout will indicate an angle in the first or fourth quadrant. It isalso known that if the order of the three values is counterclockwise,the angle is in the first quadrant. If the order of the values isclockwise, the angle is in the fourth quadrant. Likewise, if the anglemay be in the second or third quadrants, it will be in the secondquadrant if the order of the values is counterclockwise and in the thirdquadrant if the order of the values is clockwise. Readout 104, aftermaking appropriate digital calculations, will express the calculatedangle between the two sine waves. It will be understood that the numberof levels on the face of the converter may be several hundred instead ofthe limited number shown in FIG. 9.

In FIG. 10 is shown another embodiment of the invention, this onecomprising a multiplex discriminator. A multiplex signal 111 to bediscriminated and a sweep voltage 112 are placed across the deflectionplates 113, 114, respectively, of the converter. A matrix 115 comprisesa series of vertical channels, ae. Multiplex signal 111 will consist ofbits of information taken consecutively from a number of sources, inthis example five, and it is desired to separate the bits of informationfrom the five sources and send them into five separate outputs. Sweepvoltage 112, which in this case preferably will be a staircase voltagedwelling momentarily on each column, will be synchronized to return tocolumn a at the completion of five steps so that it distributes bits ofinformation consecutively across the columns a-e. Each channel ae willthen represent the output from one source. All of the output lines areled separately out of the converter, and the output lines for eachchannel a-e are fed separately out to the selector 116 which sends eachof these channel outputs to a separate recorder 117, which may be alogic store or computer memory. Each of these outputs is already pulseheight analyzed, and available immediately for further use.

FIG. 11 shows still another embodiment of the invention comprising ashaft encoder. It is desired to find the angle by which a shaft 121shown in FIG. 12, such as the azimuth bearing of a radar transmitter,varies from a zero reference level. Electromagnetic means, not shown,may be attached to the shaft itself to give a pair of signalsproportional to the sine and cosine of the angle to be detected. Theseare applied as shown in FIG. 11 to deflecting plates 122 and 123,respectively. A matrix 124 comprises in this embodimeint a circularseries of pieshaped segments around the center of the face. Eachpieshaped segment has a line leading separately to a readout comprisingtypically a lamp and an output signal to other circuits. When the sineand cosine of the desired phase angle are applied to the vertical andhorizontal deflection plates, the electron beam will be deflected tocontact one segment or possibly two. This will cause a lighting of theappropriate light in the readout circuit 125 and a signal on theappropriate line out.

The construction of the spots on the inside of the face of the cathoderay tube is shown in FIG. 13. A spout 131 of metal in the form of a thinfilm is deposited on the inside of the glass face 132 of the tube and aline 133 is extended out of the tube directly through the face of thetube. Before the metal spots are deposited, however, a high resistancefilm 134 is deposited on the inside of the glass face. The purpose ofthis is to provide a leakage path for any electrons which do not contacta conducting part of the matrix. This material is of carbon or tin oxideor various other high resistance films. It will be understood that thismaterial is not regarded as a conducting material. Its resistance perunit length is in the order of thousands of times the resistance of theconducting spots. Its purpose is to prevent a build-up of electrons onthe inside face of the glass which, if continued for a long enough time,would result in a high negative potential on the face of the tube andwould stop the operation of the tube altogether. The leakage of theelectrons on the face of the tube will be to the nearest metalconducting spot. This will cause a small level of noise on the outputsignal but this is so slight compared to the positive signals on theconducting spot upon incidence of the beam that no serious problem isencountered. It will be understood that the spots 131 may be in the formof circles, squares, lines or pieshaped segments, as shown in thevarious figures. It will also be understood that, although the cathoderay tube has been shown as constructed of glass, it may be constructedof ceramic material or, for that matter, it may be constructed of metalup to the face of the tube. Inasmuch as there is no visual output fromthe tube it is completely unnecessary to make the outer material of thetube transparent.

The construction of the solid state device may be made in a number ofways. A common method of making the device shown in FIG. 2 is to hollowout of one end of an intrinsic core a cylindrical shaft which is partlyfilled with semiconducting material of one polarity forming a base andthen filled in over that with semiconducting material of the oppositepolarity forming an emitter. Room is left for a leadout from the baseand emitter. The collector spots on the opposite end of the intrinsiccore may be deposited on the face of the core or may simply be dopedinto isolated areas of the face of the core itself. It is advisable toback the collector spots with metal and attach the outputs to the metalbacking. This prevents a situation in which a carrier beam incident upona collector spot might have to go a substantial distance throughsemiconductor material before contacting a low resistance path out. Suchan occurrence would cause a substantial reduction in the output currentand a loss of the sensitivity of the instrument.

It will be understood that the embodiments shown comprise only a few ofthe many uses for the tube or solid state device of the presentinvention. It will also be understood that various changes of thedetails, materials, steps and arrangement of parts which have beenherein described and illustrated in order to explain the nature of theinvention may be made by those skilled in the art within the principleand scope of the invention as expressed in the appended claims.

What is claimed is:

1. A signal conversion apparatus comprising:

a means for providing a beam of carriers, said means including a solidstate conversion device having an emitter composed of semiconductingmaterial of one polarity, a base connected to said emitter composed ofsemiconducting material of the opposite polarity to said emitter and acarrier transit means composed of intrinsic semiconductor materialconnected to said base at one end;

a matrix means for receiving said beam of carriers and issuing an outputcurrent in response to incidence of said beam, said matrix including acollector of predetermined configurations of semiconducting material ofthe same polarity as said emitter and attached to said carrier transitmeans at the end opposite said base; and

a deflecting means for controlling the position of said beam on saidmatrix.

2. Apparatus as recited in claim 1 wherein:

said matrix means comprises a matrix of spots of conducting material,each of said spots being adapted to receive said beam and to conduct acurrent therefrom upon incidence from said beam; and

said deflecting means comprises first means to deflect said beam inresponse to an input signal to cause a spot in said matrix to conductwhereby the position of said conducting spot is a function of theamplitude of said input signal.

3. Apparatus as recited in claim 2 further comprising:

second means to deflect said beam in a direction perpendicular to saidfirst means in response to a second input signal whereby the position ofsaid conducting spot is a function of the amplitudes of both of saidinput signals.

4. Apparatus as recited in claim 3 wherein:

said matrix means is a code matrix comprising a conductive portion in acode pattern and a substantially nonconductive portion surrounding saidpattern capable of drawing ofl electrons incident thereon;

said second means is an analog signal to be converted to a digitalsignal according to said code; and

said matrix means conducts an output current only during the time thebeam contacts a conducting portion of said matrix.

5. Apparatus as recited in claim 3 comprising:

means to apply to said first deflecting means a signal proportional to afirst sine wave;

means to apply to said second deflecting means a signal proportional toa second sine wave of frequency equal to said first sine wave;

said matrix including a center column of conducting spots each having anindividual output line, said column bisecting the collector of saidsolid state conversion device and aligned with one of said deflectingmeans;

a pair of columns of conducting lines on each side of said center columnand parallel therewith, the lines of each column extendingperpendicularly to said center column and each line having an individualoutput line; and

logic means connected to all of said output lines to detect the spotsand lines contacted by said beam and to express the phase angle betweenthe two input sine waves as a function of said matrix outputs.

6. Apparatus as recited in claim 3 in combination with an azimuthbearing whose angular position is desired to be known comprising:

means to apply to said first deflecting means a signal proportional tothe cosine of said angular position;

means to apply to said second deflecting means a signal proportional tothe sine of said angular position;

said matrix comprising a series of radially extending lines around acenter point of the collector of said solid state conversion device, oneof which is contacted by said beam so as to be conducting; and

means to detect that line which is conducting and express it as theangular position of said bearing.

7. Apparatus as recited in claim 3 wherein:

said matrix comprises a succession of columns of spots, each columnrepresenting a single channel output;

said first means comprises a sweep voltage adapted to cause the beam tocontact each channel in succession recurrently; and

said second means receives a multiplexed input signal comprising aseries of bits taken in succession recurrently from a number of sourcesequal to the number of channels in said matrix;

whereby the output of each channel corresponds to the signal from one ofsaid sources.

8. Apparatus as recited in claim 2 wherein:

said input signal is a variable sweep voltage adapted to cause the beamto pass recurrently across the collector of said solid state device;

said input signal being operable by an input pulse to cause the beam toreturn to a predetermined side of said matrix from which it sweepsacross the matrix;

said matrix comprising a row of spots of conducting materialsuccessively contacted by said beam;

whereby the output from each spot is a pulse delayed in time from theinput pulse by the time necessary for the beam to travel across thematrix from said predetermined side; and

means to select one of said outputs as a delay output pulse.

9. Apparatus as recited in claim 1 wherein said deflecting meanscomprises:

sweep voltage means to deflect said beam across said matrix recurrentlyin response to an input sweep signal; and

deflecting means aligned perpendicularly to said sweep means and adaptedto deflect said beam in response to an analog input signal;

whereby the output of said matrix is a function of said input sweepsignal and said analog input signal.

10. A signal conversion device comprising:

a cathode ray tube having a target face and an electron gun positionedat one end thereof for providing a beam of carriers;

first and second deflecting means for deflecting said beam of carriers;

a matrix means for receiving said beam of carriers and issuing an outputcurrent in response to incidence of said beam, said matrix meansincluding a center column of conducting spots each having an individualoutput line, said column bisecting said tube face and aligned with oneof said deflecting means, and a pair of columns of conducting lines oneach side of said center column and parallel therewith, the lines ofeach column extending perpendicularly to said center column and eachline having an individual output line;

means to apply to said first deflecting means a signal proportional to afirst sine wave;

means to apply to said second deflecting means a signal proportional toa second sine wave of frequency equal to said first sine wave; and

logic means connected to all of said output lines to detcct the spotsand lines contacted by said beam and to express the phase angle betweenthe two input sine waves as a function of said matrix outputs.

11. A signal conversion device comprising:

a cathode ray tube having a target face and an electron gun positionedat one end thereof for providing a beam of carriers;

a matrix means for receiving said beam of carriers and issuing an outputcurrent in response to incidence of said beam, said matrix including asuccession of columns of spots, each column representing a singlechannel output;

deflecting means including a first means having a sweep voltage adaptedto cause the beam to contact each channel in succession recurrently anda second means for receiving a multiplexed input signal comprising aseries of bits taken in succession recurrently from a number of sourcesequal to the number of channels in said matrix;

whereby the output of each channel corresponds to the signal from one ofsaid sources.

References Cited UNITED STATES PATENTS 2,417,450 3/1947 Sea-rs 3158.52,498,081 2/1950 Joel et a1 3158.5 2,517,712 8/1950 Riggen 315-8.52,534,372 12/1950 Ring 3158.5 2,616,060 10/1952 Goodall 315-8.52,916,660 12/1959 Ketchledge 315-85 2,934,673 4/1960 MacGriif 3158.52,991,459 7/1961 Darois 340347 X 3,095,517 6/1963 Fyler 315-8.5

MAYNARD R. WILBUR, Primary Examiner.

G. EDWARDS, Assistant Examiner.

US. Cl. X.R.

313 94, 346; 31s-s.s

